The invention relates to a cutting tool, particularly for steel sheet billets, including a cutting blade and an associated pressure cushion which cooperates with the cutting blade to deflect the blade edge during a punching stroke.
Cutting tools of this type, as they are known, for example, from German Patent Document DE 101 40 496 A1, U.S. Pat. Nos. 3,137,188 A or 4,607,553 A for the punching of sheet-type material, usually plastic material or cardboard, to be punched contain a hollow-cylindrical cutting blade which is sharpened on one side or in a V-shape and which, while not requiring a countertool, requires only a relatively hard supporting surface of the material to be punched, according to U.S. Pat. No. 3,137,188 A, a rubber cushion being arranged in the hollow cross-section of the cutting blade, which rubber cushion operates as a blank holder and ejector for the cut-off part of the punched material. In the case of such cutting tools, the problem arises that, during the passage of the cutting blade, the material to be punched is displaced at both sides of the cutting blade, thus toward the punchings as well as toward the useful punched part, with the result that the useful punched parts have an unclean edge and, particularly in the case of steel sheet billets or other plastically deformable material to be punched, considerable burr formations are exhibited on the bottom side of the useful part and/or toroidal thickenings are exhibited on the top side of the useful part.
It is an object of the invention to further develop a cutting tool of the initially mentioned type such that, during the punching stroke of the cutting blade, the useful punched part receives a high-quality edge which, particularly in the case of steel sheet billets, is largely free of burrs and elevations.
According to the invention, this object is achieved by means of a cutting tool having a cutting blade fastened to a blade holder and a pressure cushion which is arranged on sides of the blade holder and, when the cutting blade penetrates into a material to be punched, is pressed onto the latter in an area of a useful punched part, wherein, by displacing the pressure cushion material during a punching stroke, the cutting blade is acted upon by pressure in a lateral direction under an increasing elastic deflection of a cutting edge of the cutting blade.
According to the invention, as a result of the targeted lateral deflection of the cutting blade edge caused by the pressure cushion, the material to be punched is displaced on one side in the direction of the punchings and an elevation-forming or burr-forming buildup of material on the edge of the useful part is thereby effectively prevented. The result is an extremely precisely cut useful punched part which is largely kept free of interfering projecting material.
In a preferred application of the invention, the cutting blade has a hollow cross-section and the useful punched part is situated on the interior side of the cutting blade edge, and the cutting blade is radially widened in the cutting edge area by the pressure cushion arranged in the cross-sectional interior of the cutting blade. In order to avoid damage to the pressure cushion during the punching stroke of the cutting blade, but simultaneously exercise high lateral deformation forces onto the cutting blade, in the relaxed position, the pressure cushion is arranged with its punched-material-side face preferably essentially flush with the cutting plane of the cutting blade. If the cutting blade is bevelled in the direction of the cutting edge, the bevelling is preferably situated on the side facing away from the pressure cushion, the cutting blade, with a view to an improved cutting quality for fibrous material to be punched, expediently having an additional chamfering on the side facing the pressure cushion in the direction of the cutting edge. For reasons of an improved elasticity behavior, the cutting blade may be provided with at least one parting line extending to the cutting edge.
In a particularly preferred manner, the cutting blade consists of flexible band steel, specifically of a super-high-strength nickel chromium steel of a high elasticity, which has an excellent wear resistance and penetrates even stacked steel sheet billets without any problem and with a high cutting quality. The flexible characteristics of such a band steel are expediently utilized for generating different cutting geometries by means of the cutting tool in a constructively simple manner in connection with a variable fastening of the cutting blade on the blade holder.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.